This invention relates to a pallet-type, multi-station indexing machine and more particularly to such a machine wherein the pallets are conveyed by a continuously driven endless conveyor to the stations, detached from the conveyor for a predetermined time interval to allow work functions to be performed on work pieces carried by the pallets, and then attached to the conveyor for conveyance to the next station.
In the conventional pallet-type, multi-station indexing machine, a plurality of pallets are fixedly attached to an endless chain or flexible metallic belt which is indexed or intermittently driven a predetermined index distance to sequentially convey the pallets to each work station to allow work functions to be performed on the work pieces carried by the pallets. Although such machines are in use in the industry, they have disadvantages. For example, all of the pallets must be started and stopped at the same time which results in inertia problems. In addition, any inaccuracy in pallet location is cummulative since the accuracy of location of a pallet along the chassis or frame is determined by the cummulative error in the links of the chain or the links of the metallic belt from the drive sprocket to the location of the pallet. In the case of the pallet near the end of the machine where the idler sprocket is located, the error may be considerable. Moreover, a force exerted in any station tending to displace a pallet is transmitted to the chain or the belt and has a tendency to displace all of the pallets. Furthermore, the conventional machines require the work stations to be located at one of the points where the pallets come to rest and in addition, require indexing between stations or a large number of pallets, which increases the cost of the machine.
Indexing machines have been proposed wherein a continuously driven endless conveyor is employed for conveying the pallets which are detached from the conveyor at each station to allow a work function to be performed on its work piece and then attached to the conveyor for conveyance to the next station. The proposed machines of this type known to the inventor, however, have not proved to be satisfactory.